Seat cushion for back support



FIG. 1 is a perspective view of a seat cushion for back support, showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a right side elevation view thereof, the left side elevation view being a mirror image thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a bottom plan view thereof. 

The ornamental design for a seat cushion for back support, as shown and described. 